Influence of Non-point Source Pollution on Riverine Fish Assemblages in South West France

Abstract

The relationship between non-point source pollution (NSP) and fish assemblages in the Garonne basin, SW France was studied. Two independent data sets were coupled, one containing 20 physico-chemical variables and another containing 40 fish species in 84 study sites. Species were classified in guilds according to their feeding habitat and their diet composition. The physico-chemical variables were log-transformed and standardized for a factor analysis in which they were grouped into four factors which accounted for 80% of the total variability. These were named according to factor loadings (i.e. a measure of the variance of a given variable) whose absolute values were larger than 0.5. Hence, the first factor (F1) was formed by variables linked to NSP, most notably by sodium, chloride, potassium, orthophosphates, nitrites and chemical oxygen demand. The second factor (F2) was related to alkalinity (i.e. bicarbonates, calcium, conductivity and pH). The third factor (F3) included oxygen saturation rate and dissolved oxygen, and F4 combined both temperature and flow. Factor scores (i.e. weighted sums of the original variables) were then introduced in stepwise multiple regression models as explanatory variables of log-transformed fish species richness of trophic guilds. The NSP factor was significant (p < 0.05) for the following models: benthic omnivores (r2 = 0.66), all species (r2 = 0.65), total benthic species (r2 = 0.63), total water-column species (r2 = 0.57), benthic invertivores (r2 = 0.32) and water-column invertivores (r2 = 0.16). The guilds for which NSP was not significant were water-column omnivores, water-column piscivores and benthic detritivores. Thus, there was evidence of an inversely proportional association, though not causation, of NSP with species richness of riverine fish trophic guilds on a large spatio-temporal scale. Fish assemblages may respond in different ways to NSP depending on their species composition, on the region and on the scale, and not only to physico-chemical properties of water.

Fish diversity and assemblage patterns along the longitudinal gradient of a tropical river in the Indo-Burma hotspot region (Ping-Wang River Basin, Thailand)

“…The contribution of other variables, especially some of the water quality variables, should be considered in terms of point and non-point pollution sources over small scales (Ibarra et al, 2005;Orrego et al, 2009). The delineation of fish assemblage patterns enhances the understanding of fish zonation in this region.…”

“…This indicator is an integrative descriptor of the animal community, influenced by a large number of natural environmental factors as well as anthropogenic disturbances, including the geological history of the area, environmental stability, ecosystem productivity and heterogeneity (Lenat, 1988;Céréghino et al, 2003;He et al, 2010). It is suggested that if the physical aspects of the stream are relatively stable, they are responsible for the consistent pattern in biological community structure (Orrego et al, 2009) even though some other factors may have an influence, such as competition, predation, point, and non-point pollution sources (Ibarra et al, 2005;Orrego et al, 2009) as well as hydraulic stress (Welcomme et al, 2006).…”

Spatial and temporal variation of fish assemblages and their associations to habitat variables in a mountain stream of north Tiaoxi River, China

“…The release of non-treated domestic liquid water near human settlements, non-point pollution source from agricultural fields and factories, as well as embankment and weirs with concrete may lead to changes in the aquatic ecosystems (Walser and Bart 1999;Gerhard et al 2004;Ibarra et al 2005;Allan and Castillo 2007). Moreover, the information on fish assemblages relating to their habitat variables or anthropogenic activities is also poorly understood in East Tiaoxi River (Mao and Xu 1991; Zheng and Jia 1988).…”

Patterns of fish community composition along a river affected by agricultural and urban disturbance in south-central Chile

“…Recently studies (Habit et al, 2005) documented dramatic changes during the last decade in the fish communities in the middle section of the Biobio River such a rapid shift in fish community zonation attributed to increases in human activities along the watershed including sewage and pulp mill discharges; however, no cause-effects relationships were demonstrated. Fish community stability can be highly affected by point and non-point sources of pollution associated with land use (Ibarra et al, 2005), and in the case of Andean rivers in Chile, most land use activities involve agricultural and urbanization of watersheds. Anthropogenic disturbances such as inputs of contaminants and nutrients, heavy loading of silt and suspended matter, and episodic temperature regimes can destabilized systems resulting in decreases in the diversity and abundance of biological communities (Death & Winterbourn, 1995).…”

“…In addition, the patterns of fish community structure in lotic systems can be influenced by other biological factors (such as competition and predation), physicochemical factors such as water flow, channel morphology, habitat (Capone & Kushlan, 1991;Jackson et al, 2001), and point and non-point pollution sources (Dauba et al, 1997;Ibarra et al, 2005). The influence of non-point source pollution on fish community structure is controversial and difficult to evaluate (Ibarra et al, 2005), especially due to the low probability for establishing definitive causal relationships. Both natural and anthropogenic factors can affect habitat stability of fish communities (Alay et al, 1995), altering the normal structural and functional dynamics of fish communities along a spatial gradient.…”